The present invention relates to a device and method for collecting and quantifying sebum content on a patch of skin, to determine the natural presence thereof.
Epidermal or skin-surface fat, also known as sebum, cannot be said to consist of any one substance. It mainly consists of the secretions of the sebaceous glands, the fat of the keratinous layer and remnants of perspiration. Sebum forms a thin film that coats the skin and is generally formed at both the sebaceous glands and in the keratinous layer before exposure to secondary influences after secretion. Schaaf, F: Probleme dermatologischer Grundlagenforschung, Dr. Alfred Huthig-Veriag, Heidelberg, 1969. (Basic Research Problems in Dermatology.)
Sebum film has a number of important functions in the skin's protective mechanisms. For example, it affects the skin's permeability and absorptivity of water. It protects against environmental threats, limits evaporation thus preventing excessive drying, and affects the penetration of pharmaceutical preparations and other active or non-active substances. Deprived of this lipid containing film, the epidermis would lose its moisture at an accelerated rate resulting in dry, chapped, scaly skin conditions and the loss of suppleness. See Schneider, W., Die Bendeutung, Experimenteller Untersuchungen des Lipid-Wasser-Gehaltes an der Haut fur die externe Therapie, Derm. WSCHR., 147, 1963, pp. 1-7. Concerning the significance for external treatment of experimental work on the lipid and water content of skin.
Hence, the measurement of the natural presence of sebum on human skin, and particularly facial skin, is a problem of current interest among dermatologists, pharmaceutical manufacturers and cosmetics manufacturers. The cosmetic industry is particularly interested in such measurements since the quantitative assessment of skin oiliness enables the beautician or cosmetics sales clerk to recommend an optimal assortment of cosmetics.
In cosmetics, pharmaceuticals, and dermatology, different types of apparatus exist for measuring the amount of sebum secreted by the skin of a living subject. Most of these apparatus are based on the fact that when sebum is deposited on a translucent element, such as a frosted glass or plastic plate or strip, the element becomes increasingly transparent (the greater the amount of sebum applied, the greater the transparency produced). One method of measurement consists of subjecting the sebum covered translucent element to a luminous flux and measuring the amount of light which passes through the translucent element by the use of a photoelectric receiver. Schafer, H. und Kuhn-Bussius H., Methods regarding quantitative Determining of Fat Secretion. Archives of the Clinical-Experimental Dermatology, 238. 429-435, 1970.
The quantitation of sebum secretion in human skin has been the basis for most of the photometric apparatus and methods used to date. Light transmission through opalescent (frosted or ground) glass is increased when the rough surface is fatted with sebum. There is a constant relation between the change of the transmission and the weight of fat upon the frosted glass elements being pressed to the forehead. By comparing the measurements of known amounts of petrolatum distributed on the forehead, quantitative measurements of the casual level of surface fat related to the function of the sebaceous gland secretion has been obtained. This observation has prompted a number of patents describing apparatus of various types that are suitable for clinical measurements of sebum. These patents include: French Patent Nos. 2,368,708; 2,404,845; United Kingdom Patent Nos 1,590,598, 2,022,818 and 2,043,886; and U.S. Pat. Nos. 4,480,921 and 4,483,619.
U.S. Pat. 4,494,869 is based on a modification of the principles stated above. A smooth, optically clear lens is contacted with the skin to collect droplets of sebum on its sampling surface. Then, light emitted from an optical source is passed through the sampling surface and focused onto an optical detector. The output signal of the detector is displayed to give an indication of the degree of oiliness or sebum content of the skin.
A technique of Strauss and Pochi uses parts of ether-extracted cigarette paper to collect sebum as the function of time. The collected sebum is determined gravimetrically. Strauss, J. S., Pochi, P. E.: The Quantitative Gravimetric Determination of Sebum Production. J. Invest. Dermatol. 36:293-298 (1961).
A technique of Downing, Stranium, and Strauss uses a bentonite absorbent to collect sebum that is then assayed by thin layer chromatography. Downing, D. T., Stramen, A. M., Stauss, J. S., The Effect of Accumulated Lipids on Measurements of Sebum Secretion. J. Invest. Dermatol. 79:226-228 (1982).
However, none of the above-cited methods lends itself to use by a cosmetician or a salesperson, a doctor, or a pharamacist outside of a clinical laboratory.
The "Sebumeter", described in German Offenlegungsschift 2,353,224, has been developed to facilitate the sebum sampling operations. See also, Schrader, K: A New Procedure for the Determination of Skin-Surface Fat. Dracogo Report, 8/74, pp. 171-174. This apparatus requires very little training on the part of the operator and consists of two separate components; namely a sampling device, and a measuring device which is equipped with a photoelectric receiver and a source of illumination. The sampling device comprises a casing, from which projects a sample-holder on which the translucent element (plastic tape) is arranged. The sample-holder is connected to the casing by a calibrated spring to enable the sample-holder to be applied, under an approximately constant pressure, to the patch of skin to be studied. After having sampled the sebum, the sample holder is carried into the photoelectric measuring device of the apparatus in order to evaluate the amount of sebum secreted. Although the "Sebumeter" represents an improvement over the other above-cited references, it still has numerous problems and limitations. For example, the contact time at a rather high pressure is 30 seconds. This can become somewhat tedious when dozens of tests, including the preparation and repreparation of the apparatus, are conducted per hour. Further, the apparatus is costly and requires the continual purchase of a cassette containing the plastic film sampling device which is also fairly costly, particularly when the usage of this machine at a cosmetic counter could well exceed 100 tests in a few hours.
There have been some attempts along the lines of a litmus or pH paper type device, namely U.S. Pat. No. 4,313,393, which describes an indicator device for determining the dry, normal, and oily characteristics of human hair and scalp. The apparatus comprises an oil absorbent indicating material, treated with an oil soluble dye and surrounded by an oil permeable membrane. See also U.S. Pat. No. 4,313,393, 2/1983, Barbuscio et al. However, investigation of the disclosed process and apparatus has indicated several problems with the technique including : (1) the indicator was designed for hair and scalp and if used on face and forehead, the oil soluble dye could likely come in contact with the skin, and cause irritation, and the dye could also transfer to and discolor the skin; (2) the level of oiliness is estimated as a function of the depth of the color developed. Frequently it becomes difficult and confusing for the users or consumers to analyze their skin type such as normal, oily, and dry conditions, by this type of subjective analysis. Further, a color-based analysis is particularly impractical for those who are color blind; and (3) the method of affixing the laminated device to the skin is tedious and unattractive.
U.S. Pat. No. 4,532,937 (European Patent No. 129598) represents an improvement over the indicator device described above. It describes an accurate and simple device for collecting sebum as it is secreted. It is comprised of an open celled, microporous, hydrophobic polymeric film, coated with a special pressure-sensitive adhesive that does not migrate into the micropores of the film. The film is affixed to the skin by means of the adhesive, thus making it similar to an adhesive bandage. As sebum is secreted from the skin, it can flow through the adhesive into the pores of the film. Originally the film is opaque-to-light or opalescent in appearance. It will become substantially translucent when the pores are filled with sebum. The level of transparency is proportional to the quantity of oil absorbed from the skin contact site which is controlled by the amount of sebum present on the skin. A commercial indicator device based on this patent is currently marketed under the trade name SEBUTAPE (trademark of Cuderm Corporation, Dallas, Tex.).
To facilitate the reading of the level of sebum collected (intensity of translucency), several convenient reference patterns of various intensities are provided. The user removes the tested tape and places it on a black background that is provided. The pores of the tape that are filled with sebum will become more visible as multiple black color dots patterns. Comparison with a precalibrated reference pattern for skin type allows definition of the type of skin (i.e. the amount of sebum generated). The directions accompanying this device require facial cleansing to establish a reference point which is followed by taping over six recommended facial sites (right and left forehead and cheek, as well as nose and chin). The six film strips with adhesive backings have to remain on the test sites for at least one hour. Example 1 of the U.S. Pat. No. 4,532,937 cites 3 hours of application. This patent claims the combination of using the unique feature of the adhesive on a microporous, hydrophobic polymeric film which is made by Celanese and marketed as Celgard .RTM. grade 2400.
Despite its simplicity and advantages over other methods, this device has considerable drawbacks which are preventing general acceptance and use by consumers, namely: (1) it is extremely inconvenient and tedious for users to function with several adhesive-backed plastic strips stuck on several facial test sites for up to three hours; (2) no matter how benign the adhesive is, users with a sensitive skin would suffer inconvenience and temporary irritation from such a lengthy exposure; and (3) the overall cost is still relatively quite high.
To meet the needs of the large number of cosmetics users and dermatology patients, and at the same time, facilitate the job of beauticians, sales clerks, doctors, and pharmacists, an indicator along the lines of litmus or pH paper is badly needed. The device should combine simplicity, accuracy, ease of use, safety, and low cost. To date, such criteria have not been met, and as a result no indicator type device is enjoying wide acceptance.
It is obvious that if the problems associated with such a device could be eliminated, the resulting indicator device would meet the ideal product criteria. Furthermore, it would lend itself to dissemination through inserts in magazine ads, permitting the user to perform the necessary skin oiliness measurement and then order the recommended products for a specific skin condition.